diff --git a/grass-gis-test-docker/Dockerfile b/grass-gis-test-docker/Dockerfile
index 8f5cba2..bcccbad 100644
--- a/grass-gis-test-docker/Dockerfile
+++ b/grass-gis-test-docker/Dockerfile
@@ -8,10 +8,14 @@ COPY test-docker/test.sh /src
 
 RUN test -e test-docker/ && rm -rf test-docker/
 
-RUN apk add gcc make python3-dev musl-dev linux-headers
-
-# create environment to install requirements
-RUN python -m venv addon-env
+# Pin Python to 3.12 (from Alpine 3.20 compat repo) to avoid the
+# multiprocessing forkserver regression in Python 3.14 which breaks
+# GRASS's temporal RPC server (grass/pygrass/rpc/base.py thread_checker).
+# The forkserver address file is no longer found on Process.start()
+# in Python 3.14, causing FileNotFoundError during server restart.
+# See: https://github.com/mundialis/v.alkis.buildings.import/pull/30
+RUN apk add --no-cache python3.12 py3.12-pip python3.12-dev gcc make musl-dev linux-headers
+RUN python3.12 -m venv addon-env
 ENV PATH="/src/addon-env/bin:$PATH"
 RUN test -e requirements.txt && pip3 install -r requirements.txt || echo "No requirements.txt"